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March 31, 1964 R, H, BLQQD 3,126,962

OIL RECOVERY METHOD Filed Aug. 11, 1960 2 Sheets-Sheet 1 Robert H. Blood Invenor March 3l, 1964 R. H. BLOOD t 3,126,962

OIL RECOVERY METHOD Filed Aug. 11, 1960 2 sheets-sheet 2 fou'.

FIG. 2

Robert H. Bloocl Inventor WQ Attorney United States Patent O 3,126,962 @EL RECOVERY METHD Robert H. Blood, Tulsa, Ghia., assigner to iersey Production Research Company, a corporation of Delaware Filed Aug. 11, 1950, Ser. No. 41921 9 Claims. (Cl. ld-42) This invention refers to a method for recovering oil from subterranean reservoirs. More particularly, it refers to a secondary method of oil recovery from dipping reservoirs using a single well.

Briefly, this invention refers to a method of oil recovery from relatively small reservoirs wherein the oil reservoir is c-losed or trapped by local deformation of the strata. Typical of such reservoirs are those that are closed by folding, or combinations of faulting and/or folding, etc. Of current interest, however, are small dipping traps-eg., reservoirs that have been formed by the upward movement and formation of a salt dome. Typically strata involving such oil reservoirs are arched upward into a dome upon being pierced by the salt. The deformation of the beds causes severe faulting. As a result of this there is a complicated structural pattern which usually creates one or more steeply dipping reservoirs. In many instances, the reservoirs are between overlying and underlying relatively impermeable formations, which, in combination with the relatively impermeable salt, afford an ideal condition for trapping oil. The oil tends to move up-dip until it encounters the salt, lwhere its upward movement is arrested. ln many instances the extent of trapped oil is not sufficient to make economical the usual secondary recovery methods requiring one or more injection wells and one or more producing wells.

`Accordingly, it is an object of this invention to provide a method of oil recovery which will apply to reservoirs of the above character.

It is another object of this invention to provide a method of oil recovery wherein a single well is used for both injection of dri-ving tluids and oil production.

A further object of this invention is to provide a method of oil recovery from dipping formations wherein the oil is forced to migrate upward and/ or down-ward into a single well.

A still further object of this invention is to provide a drive method of oil recovery wherein oil is forced to a single production well -by driving iluids injected through the same well into the reservoir -up-dip and/ or down-dip.

These and other objects of this invention will become more apparent upon further reading of the specification j and claims when taken in conjunction with the following illustrations of which:

FfGURE l is a cross-sectional view of a combined injection and production apparatus useful in the method of this invention, and in particular that process wherein driving iiuid is injected from a production well so as to enter the reservoir a distance down-dip from the well to force the oil upward Iwithin the reservoir toward the production well.

FIGURE 2 is a similar cross-sectional view showing an additional embodiment of this invention wherein driving fluid is injected from a production well so as to enter the reservoir a distance up-dip from the well to force the oil downward within the reservoir toward the production well.

Referring now to FIGURE l in greater detail. As a typical example of use, a dipping oil reservoir l@ is trapped between relatively impermeable strata 14 and 16 and capped by the salt dome l2. At some point downdip within the oil reservoir lil a water level 1S may exist. The point or approximate point of the oil-water inter- 3,126,962 Patented Mar. 3l, 1964 ICC face may be determined from available reservoir information, etc. An existing Well or a new well Ztl is drilled at least through the oil reservoir and preferably at least to a depth corresponding to the level of the oil-water interface. Using typical well completion techniques, a casing 22f is affixed Within the well using cement 2.4. Tubing 26 is positioned within the -well using a packer and anchor means 23 to form annular space 29. Either prior to or after placement of tubing Z6 and packer 2S directional communication 3ft is created from the well to the reservoir vllt? through the relative impermeable underlying strata d6 usinfy techniques which are well known in the art. -For instance, apparatus and services are now available capable of directionally perforating or initiating fractures in a given oriented direction. Where directional perforation is used, hydraulic -uid pressure is thereafter created within the per-foration -to lift the overburden and extend fracture 3d at least through the impermeable strata and into the oil reservoir, preferably at or below the oil-water interface. In some instances the fracture is carried into the reservoir proper to aid the injection of uid into reservoir it). The fracture once created is held open by high strength propping agents which permit a relatively permeable path, from well to reservoir, for the injection fluids.

A shaped charge or bullet type perforating gun may be used to perforate the casing 22 and cement 24 to provide communication from oil reservoir 1d into the annular space 29 ofthe well. For maximum recovery efficiency the perforations 3x2 are placed opposite the upper part of the oil stratum within reservoir 10.

in operation, a driving iluid of density `greater than the oil, such as water, is injected into tubing 26 from a remote source or from a subterranean source within well itl. Flow continues through fracture 3?l into reservoir lil, preferably into the water zone 1S. Cellar oil, i.e., oil down-dip of the well, is displaced toward well Ztl, into perforations 3-2 where it is lifted to the surface under natural flow conditions or by artificial means such as pumping, gas lift, etc.

Reference is now made to FIGURE 2 where like numerals are used to denote like apparatus and features as described in yFIGURE l. Similarly a single well injection and production system is provided with particular reference to production of attic oil, i.e., oil up-dip from the well. In this embodiment, fracture 30 is directionally and substantially horizontally created through the overlying impermeable strata 14 to the oil reservoir gas space 34. Natural gas, LPG., tine-gas, carbon dioxide or other lighter-thanoil `fluids or combinations thereof are injected into the annular space 29 between casing Z2 and production tubing 2.6. `Continued injection forces oil to migrate down-dip into perforations 3Q.. In this instance perforations 32 are placed opposite the lower part of reservoir lt). The oil is produced through tubing 215.

Although the embodiments of FGURES l and 2 are shown and described separately, this is not to be held limiting. The attic and cellar oil recovery methods, for example, can be combined using a single well injection and production apparatus.

It is to be understood that the apparaus shown by the views is simplified 4for descriptive purposes. Other well known combinations of packers, tubing and so on can be used for a combined single well injection and production system.

Although the invention has been described with reference to specific and preferred embodiments, it will be apparent that many modifications can be made without departing `from the spirit of the invention. For example, perforations 32 may include fractures to establish oil production communication with reservoir lt). Accordingly,

1 far Qi this invention should be construed not to be limited to the embodiments herein described, but should be limited only by the scope of the appended claims.

Whatis claimed is:

1. A method of producing oil from a dipping subterranean reservoir located between overlying and underlying relatively llow permeability strata and penetrated by a well having irst and second conduits therein, comprising the steps of providing iirst directional communication through said under-lying strata in a down-dip direction from said well to at least said reservoir, providing second communication from said well opposite said reservoir, connecting -said lirst conduit in said well with said lirst communication and connecting said second conduit in said well with said second communication, injecting a tluid of density greater than said oil into said reservoir through said iirst conduit and recovering oil through said second conduit.

2. A method of producing oil in accordance with the steps of claim 1 wherein said injecting fluid comprises water.

3. A method of producing oil from a dipping subterranean reservoir located between overlying and underlying relatively low permeability strata and penetrated by a well having lirst and second conduits therein, comprising lthe steps of directionally fracturing said underlying strata in a down-dip direction from said well to at least said reservoir, providing communication from said well opposite said reservoir, connecting said first conduit in said :well with said fracture and connecting said second conduit in said well with said communication, injecting a iiuid of density greater than said oil into said reservoir through said first conduit and producing oil through said second conduit.

4. A method of producing oil from a dipping subterranean reservoir located between overlying and underlying relatively low permeability strata and penetrated by a well having rst and second conduits therein, comprising the steps of directionally yfracturing said underlying strata substantially horizontally from said well to at least said reservoir, perforating said well opposite said reservoir, connecting said first conduit in said well wi-th said fracture and connecting said second conduit in said well with said perforation, injecting water into said reservoir through said first conduit and producing oil through said second conduit.

5. A method of producing oil lfrom a dipping subterranean reservoir located between overlying and underlying low permeability strata and penetrated by a rwell having rst and second `conduits therein, comprising the steps of fracturing said overlying strata in a horizontal direction from said well to at least said reservoir, perforating said well opposite said reservoir, connecting a lirst conduit in said well with said fracture and a second conduit in said well with said perforation, injecting a fluid of density less than said oil into said reservoir through said first conduit and recovering oil through said second conduit.

6. A method of producing oil from a dipping subterranean reservoir located between overlying and underlying low permeability strata and penetrated by a well having first and second conduits therein, comprising the steps of directionally yfracturing said overlying strata horizontally from said well to at least said reservoir, perforating said well opposite said reservoir, connecting a first conduit in said Well with said fracture and a second conduit in said well with said perforations, injecting a fluid misc-ible with said `oil into said reservoir through said first conduit and recovering oil through said second conduit.

7. A method of producing oil according to claim 6 wherein said miscible lluid is L.P.G.

8. A method of producing oil from a dipping subterranean reservoir located between overlying and underlying low permeability strata and penetrated by a well having irst, second, and third conduits therein, comprising the steps of directionally fracturing said overlying and underlying strata horizontally yfrom said Well to at least said reservoir, perforating said well opposite said reservoir, connecting a iirst conduit in said well with said fracture in said overlying strata, connecting saidsecond conduit with said underlying strata, connecting said third conduit with said perforations, injecting a fluid of density less than said oil into said first conduit, injecting a fluid of density greater than said oil into said second conduit and recovering oil through said third conduit.

9. A method of producing oil from a dipping subterranean reservoir `by means or a iluid having a density different than the oil, said reservoir being positioned between an overlying low-permeability stratum and an underlying low-permeability stratum and penetrated by a well having irst and second conduits therein, which comprises the steps of establishing a first substantially horizontal zone of communication between said first conduit and said reservoir through a first said stratum, said irst stratum being said overlying stratum when said fluid is less dense than said oil and being said underlying stratum when said fluid is more dense than said oil, establishing a second zone of communication directly between said second `conduit and said reservoir, said second zone of communication being vertically spaced from said first zone of communication, thereafter injecting said iiuid through said irst conduit and said first zone of communication into said reservoir, and recovering oil from said reservoir through said second zone of communication and said second conduit.

References Cited in the tile of this patent UNITED STATES PATENTS 1,885,807 Doherty Nov. 1, 1932 -2,821,255 `Spearow Jan. 2'8, 1958 2,862,556 Tek o Dec. 2, 1958 3,020,954 Graham et al. Feb. 13, 1962 

1. A METHOD OF PRODUCING OIL FROM A DIPPING SUBTERRANEAN RESERVOIR LOCATED BETWEEN OVERLYING AND UNDERLYING RELATIVELYLOW PERMEABILITY STRATE AND PENETRATED BY A WELL HAVING FIRST AND SECOND CONDUITS THEREIN, COMPRISING THE STEPS OF PROVIDING FIRST DIRECTIONAL COMMUNICATION THROUGH SAID UNLERLYING STRATE IN A DOWN-DIP DIRECTION FROM SAID WELL TO AT LEAST SAID RESERVOIR, PROVIDING SECOND COMMUNICATION FROM SAID WELL OPPOSITE SAID RESERVOIR, CONNECTING SAID FIRST CONDUIT IN SAID WELL WITH SAID FIRST COMMUNICATION AND CONNECTING SAID SECOND CONDUIT IN SAID WELL WITH SAID SECOND COMMUNICATION, INJECTING A FLUID OF DENSITY OF GREATER THAN SAID OL INTYO SAID RESDRVOIR THROUGH SAID FIRST CONDUIT AND RECOVERING OIL THROUGH SAID SECOND CONDUIT. 